1. Field of the Invention
The present invention relates in general to a midsole of a shoe having a shock absorber or a cushion and a method for preparing such a midsole, and more particularly to a midsole having a bellows type of air bag as the shock absorber and a method for preparation of such a midsole.
2. Description of the Prior Art
A known shoe such as a sports shoe is generally provided at its outer sole with a resilient midsole which is to absorb the pressure, said pressure intending to be transferred from the ground to the sole of wearer's foot when the wearer takes a step forwards in the course of walking or running, in this respect, to prevent the wearer's foot from suffering from the pressure and to provide the comfort of the wearer. In order to provide such a resilient midsole for the shoe, the outer sole of the shoe is conventionally provided with a sponge midsole, a combined foam midsole and a midsole enclosing a closed bag-shaped air bag.
However, it is noted that the known shoe having aforementioned midsole, that is, the sponge midsole, the combined foam midsole and the midsole enclosing the closed bag-shaped air bag, has a disadvantage in that the cushioning of the midsole can not be freely controlled in order to correspond to the using object of the shoe and the resilience of the midsole is relatively lower than it is conventionally required.
The above disadvantage of the shoe having the known midsole is necessarily caused by uniformly manufacturing the midsole and equipping the shoe with this midsole regardless of the conditions in practically using the shoe such as using object of the shoe, the wearer's weight and the like. In other words, while the resilient midsole manufactured by the aforementioned process provides somewhat shock absorbing effect for the shoe, it also introduces several problems. For example, the air bag, having a bag-shaped outer appearance as it is prepared by a conventional preparation method wherein the previously cut raw materials are simply welded to each other using a high-frequency resistance welder, necessarily has a substantially larger welding area than it is needed to improve the cushioning effect of the midsole. In addition, if this type of air bag is charged with air, its swollen shape shows an inclined bag-shaped outer appearance and, in this respect, its volume is necessarily reduced and this causes the shock absorbing effect of the air bag to be deteriorated. Furthermore, in consideration of the known manufacturing process wherein the air bag is uniformly manufactured and equipped to the shoe regardless of the conditions such as using object of the shoe, the wearer's weight and the like, the practical shock absorbing effect of the air bag is deteriorated.